Remote radio receiver tuning indicating apparatus



2,654,651 REMOTE RADIO RECEIVER TUNING INDICATING APPARATUS Filed Oct. 29, 1945 J. G. BLACK oct. 6, 1953 5 Sheets-Sheet l 2,654,651 REMOTE RADIO RECEIVER TUNING INDICATING APPARATUS` Filed oct. 29, 1945 J. G. BLACK Oct. 6, 1953 I5 Sheets-Sheet 2 www Oct. 6, 1953 1 G, BLACK 2,654,651

REMOTE RADIO RECEIVER TUNING INDIATING APPAEATUS Filed OCT.. 29, 1945 5 SheeS-Sh'ee'fI 5 Patented Oct. 6, 1953 REMOTE RADIO RECEIVER TUNING INDICATING APPARATUS James G. Black, Chicago, Ill.,

Compenso Chicago,

Nielsen of AIllinols assigner to A. C. Ill., a corporation Application October 29, 1945, Serial No. 625,371

9 Claims.

The present invention relates to remote radio provision of new and improved apparatus of the aforesaid character.

Another object of the present invention is the provision of new and improved apparatus for inowncr of the receiver.

A further object of the present invention is to provide new and improved radio receiver tuning indicating apparatus including means for accurately indicating the tuning of a radio receiver, which means is operatively connected to the radio receiver through a suitable line, such as a telephone line.

A further object of the present invention is the provision of a new and improved remote radio receiver tuning indicating apparatus comprising a balanced circuit including a telephone line or the like and variable impedance means associated with the radio receiver whose tuning is to be indicated and which unbalances the circuit when the tuning is changed and other variable impedance means located at a central station which is operated to rebalance the circuit.

A further object of the present invention is to provide a new and improved apparatus of the character set forth in the preceding paragraph including motor operated variable resistors associated both with the radio receiver and with the central station apparatus.

A further object of the present invention is to provide a new and improved tuning indicating apparatus including a balanced circuit and means for substantially unbalancing the circuit when the tuning is Varied thereby to effect operation of the indicating means over a considerable range each time the tuning is changed to provide greater accuracy.

A further object of the present invention is to provide a new and improved radio receiver tuning indicating apparatus including an indicator member moved to different positions by a motor and means for dynamically stopping the motor, thereby' t0 insure greater accuracy of indications.

Another object of the present invention is the porvision of a new and improved means for dynamically stopping a motor, and more specilically, a means including a normally charged capacitor dischargeable through a motor winding for quickly and effectively stopping the motor.

A further object of the present invention is to provide radio receiver tuning indicating appara-` tus including new and improved means for indicating when the receiver is turned oi and also when the indicating means is disconnected from the receiver, as by an open circuit in the telephone line, and further, including means for signalling the two above mentioned conditions.

Another object of the present invention is the provision of new and improved radio receiver tuning indicating apparatus including means for indicating the station to which the receiver is tuned and also the network to which the station is connected.

A further object is the provision of new and improved readily changed visual indicating means especially suited for indicating the network to which a radio receiver is tuned.

Other objects and advantages of the present invention will become apparent from the ensuing description of an embodiment of the invention in which reference is had to the accompanying drawing, in which:

Fig. 1 is a schematic representation of one embodiment of the invention;

Fig. 2 is a side elevational view of a visual indicator control mechanism utilized in the invention and which is only diagrammatically illustrated in Fig. 1

Fig. 3 is a fragmentary plan view of the mechanism;

Fig. 4 is a fragmentary vertical cross-sectional view taken generally along the line 4 4 of Fig. 2; and

Fig. 5 is an enlarged cross-sectional view taken along the line 5-5 of Fig. 4.

In brief, the present invention has for its primary purpose the indication or recording, or both, at a central station the various broadcast stations to which a radio receiver located in the home of the radio owner is tuned. It comprises a balanced circuit extending between the home and station, which circuit preferably includes a telephone line between the two locations. The balance of the circuit is changed when the tuning of a radio receiver is changed and the unbalance results in the operation of indicating or recording means at the station to a point corresponding to the newly selected station by means which restores the balance of the circuit.

The apparatus of the present invention comprises, in the main, two units, the rst of which is indicated by reference character i0 and is located at the central point or station and a second unit, indicated by the reference character l2, which is coupled to a radio receiver. The

two units are coupled to each other preferably through a telephone circuit including the conductors hi and i6. The units may be permanently coupled or may be coupled at desired or selected times through a telephone exchange, not shown.

While the iigure illustrates apparatus for indieating or recording the tuning of a single receiver, it should be understood that the tuning of any number of receivers may be recorded by similar apparatus for each of the receivers whose operation is to be indicated or recorded.

The coupling between the units l and l2 is effected primarily through a balanced circuit including the telephone lines lli and it. The balanced circuit is preferably of the bridge type and preferably includes continuously variable impedance means, such as resistors 20 and 22, associated with the radio receiver and indicating or recording apparatus, respectively. The value oi resistor 20 is controlled in response to the tuning of the radio receiver and changes in tuning effects changes the value of the resistor to unbalance the circuit. The circuit balance is restored by adjustment of resistor 22, the value of which and the position of the adjusting means of which are thus indicative of the radio station to which the receiver is tuned. The resistors may be of the rotary type and have resistances of about 10,000 ohms. Resistor 22 also has an open circuit position for a purpose which will appear hereafter.

The bridge circuit includes in addition to the telephone line and resistors 2t and 22, a pair of fixed resistors 2d and 20 and an adjustable line balancer resistor 23 connected in series with resistor 22. Resistors 22-28, 2d and 26 constitute three legs of the bridge and the fourth leg includes the resistor'Z associated with the radio receiver. Resistors 2d, 20, and 28 may also have values of about 10,000 ohms.

The bridge circuit is energized with direct current supplied to it through a pair of conductors 3U connected to a suitable source of direct current, which source may include a dry disc type rectifier 32 and a ilter 3d. The rectier is connected to the secondary winding 36 of a transformer 38, the primary winding le of which is connected to a pair of conductors e2 leading to a suitable source of alternating current, as through a power switch dit anda plug type connector 4B.

The bridge circuit has its output terminals 50 and 52 connected to indicating and recording means and to power means controlling the variable resistor 22 in a manner to be described in greater detail shortly through conductors 54 and t.

The valve of the variable resistor 20 associated with the receiver is varied in response to the tuning of the receiver and unbalances the bridge circuit when the tuning is changed. It is preferred that its value be varied by a slow speed (such as 1 R. P. M.) unidirectional motor 60 mechanically Y connected to a movable resistor contact 6-2. The motor` may comprise a part of an electronic device coupled to a radio receiver and operable to positions indicative of the tuning of the radio receiver and 'thus to the various broadcast stations to which the receiver is tuned. This electronic device may be of the type disclosed and claimed in the copending application of Robert A. Clark,

Jr., Application Serial No. 511,246, led November 22, 1943, now Patent No. 2,483,573, and assigned to the assignee of this application. The electronic device is not illustrated nor will it be described in detail. It is believed sucient to say that it includes a relay 64 which is adapted to be energized whenever the radio receiver is turned on. This relay 1s utilized to operate a movable switch blade 66 to connect the resistor 20 to the bridge circuit when the relay is operated. When operated, switch blade 60 interconnects telephone line I4 and a conductor E8 leading to the movable contact 62 associated with resistor 20.

The electronic device also includes the previously referred to motor 60 mechanically connected to a variable capacitor 'i0 forming part of the electronic control. The motor is so controlled that it is energized, when the tuning of the receiver is changed, to operate the capacitor 10 to a point corresponding to the station to which the receiver is tuned. When this point is reached, the motor is deenergized and stopped. 1t will thus be apparent that the value of resistor 20 is indicative of the station to which the receiver is tuned. The motor 60 is supplied with power through a pair of conductors 'l2 under the control of the electronic control device.

The unit l2 of the present invention associated with the receiver also includes means for unbalancing the bridge to a predetermined and unique extent to provide an indication of the operativeness of the radio receiver, thereby to provide an indication of the on and off periods of the receiver. This means includes an adjustable resistor 14, the value of which is preadjusted by means of a movable contact 'i5 and which is substituted in the bridge circuit for resistor 20 when the radio receiver is turned off. The substitution is effected by the relay ed, the switch blade 00 of which connects telephone line ifi to the resistor through conductor 18 when the radio is turned oi and the relay 6d is deenergized. The relay Gli may remain energized for a brief period after the receiver is turned off because of a delay in the cooling of a cathode of a rectifier tube, provided a tube using an indirectly heated cathode is used, as is used in the disclosure of said application. As a result the motor operates for a brief period when thereceiver is turned ofi", and varying resistor 20-but this is not a disadvantage because of the substitution of the Off resistor lli when the relay is deenergized. Rather, the delay is an advantage because when the receiver is subsequently turned on the motor operates and changes capacitor l0 and resistor 20 to return these to Values and positions corresponding to the station tuned before the set was turned ofi. The resistor 'ld may have a value of about 10,000 ohms,

- of which about 6,000 ohms are used.

In order to increase the accuracy of the apparatus, means are provided for insuring that the indicating means is operated to a substantial eX- tent each time the tuning of the receiver is varied. This means substantially unbalances the bridge circuit each time the tuning is varied. It includes a relay connected in parallel with the motor 5c and therefore energized each time the motor is energized, i. e., each time the tuning of the receiver is varied, and a circuit unbalancing resistor S2. placed in the bridge circuit by the relay when it is energized. The resistor 82 is connected to telephone line l5 and to a conductor 84 leading to the common ends of the resistors 2li and 14. When the tuning is changed and the motor 00 energized, the resistor 82 is placed in circuit by operation of switch blade 80 of relay 80, which removes a short circuit from across the resistor. When the short circuit is thus removed, the resistor 82 isV placed in series with the resistor 20 to accises-1 unbalancel the bridge circuitand to effect operation oi.'V the indicatingmeansover a considerable range. The resistor 82 may have a value of about 30,000 ohms.

The indicating or recording: station unit I includes means for indicating and preferably recording the station to which the radio receiver is tuned. This means includes a tape type recorder 90 having a movable indicator-scriber 92 operated into diiierent positions corresponding to the tuning of the radio receiver by a unidirectional alternating current motor 9-4 placed into operation when the circuit is unbalanced and which is also mechanically connected to-the movable contact 96 of the variable resistor 22 to correlate the position of the scriber 92' with the position and valueof resistor 22- and thus to the tuning of the radio receiver.

The tape type recorder 90 may be of1various types and has therefore not been illustrated in detail. It may', however, include, anY electrical and spring type drive and speedY reducing unit 98 for driving the tape |00 at a constant speed. More specically, the stylus arm 02 is mounted for universal movement at its end 92a and is adapted to be moved to bring its stylus S21) thereof into engagement with the tape |00 in response to energization of a magnet 200. Movement of the stylus 92h transversely of the tape |00 to positionsv corresponding to stations to which the` re-V ceiver I2 is tuned is effected by crank` connecting the stylus arm 92 by means of a crank |9419 to a crank wheel |94a mounted for rotation with the drive shaft of the motor 94'.

The motor 8f3 is placed into operation to move the scriber 92 and to adjust resistor 22 whenever the bridge circuit is unbalanced. This control is effected through a motor circuit controlling relay |02 including a pair of switch blades |04 and |06, and a relay |08, preferably of the polarized type and including a movable switch blade H0,

unbalance of the bridge. The relay |08 includesa Winding ||.2 which` is energized whenever the bridge circuit is unbalanced in either direction.

In order to increase the sensitivity of the apparatus, the bridge circuit is coupled. to the relay |68 though an amplier indicated asl a whole by reference character 4 and including a pair of electron tubes I la and l. l 8. The tubes are preferably of the 6 5 6 type and they are connected in differential relationship to the bridge circuit and to a relay winding |2 (having an impedance of about 6,000 ohms), which is connected across the anodes of the two tubes through a resistor (having a value of about 5,000 ohms). Suitable anode potential is applied to the anodes of the two tubes through resistors 26 and |22 (each of about 6,500 ohms), the common junction of which, is connected to an anode voltage supplying conductor |24.

The anode potential rectifying means of the a tube |26 (as oi the is preferably supplied by electronic type including 80 type) energized through a transformer |28. The filament of the tube. is supplied with power from a low voltage secondary winding |30 of the transformer. The direct current output of the rectifier is supplied to the conductor |24 through a lter circuit |32 and a voltage regulator tube |34, which may be of the X7R-15d type. The negative side of the direct current voltage is connected by conductor |36 to the cathodes of the amplier tubes ||6 and ||8 through the cathode bias resistors |38 and respectively ('each of about 1170 ohms).

The control grids ofthe tubes H6 and ||8 are connected? to. the. output terminals 5l) and 52 of tirev bridge circuitfthrough a normally closed test switch` |542, the conductors 54 and 56 and rcsi'stors |46 and |46, respectively (each of about .l megohm). rEhe grid circuits are connected to the negativeline |136 through resistors |48 and |150, respectively (ea-ch of about 5,000 ohms).

When the bridge circuit is balanced, no current ilews through the windingv ||21 of the polarized relay Hi8-a condition that is obtained through the use of adjusting means including a resistor |52- (of about 500 ohms) connected across resistors |538 and |40 and an adjustable contact |54 connecting the resistor |52 to the junction of resistors 38 and |40. The adjustment is made with the testl switch |42 open', which brings about ay condition corresponding to a balanced condition or the bridge when the terminals 50 and 52 are at the same potential.

When the bridge is unbalanced, current flows in one direction or the other through the winding ||2 with the result that the relay contact H0 is moved from a normal circuit opening position to a circuit closing position to energize the winding of the relay |02. This energizing circuit eX- tends from one of conductors 30 to the other through conductor |56, which may have a voltage reducing resistor |51 interposed therein, the relax Winding, conductor |58, one or the other of |60 associated with the movable contact H0, the movable contact itself, and conductor |62.

When the winding of relay |02 is thus energized in response to the imbalance of the bridge circuit, the switch blades |04 and |06 are operated from a dynamic stopping position, which will be described in greater detail shortly, to a position to connect the motor through the pair of conductors |64, the switch blades |04 and |06,

the pair of conductors |66,

the plug type connector 46. When this circuit is closed, the motor 94 is energized and operates to adjust resistor 22 to restore the balance of the bridge circuit and to move the soriber 92 to a position corresponding to the pisition of contact 96 and the value of resistor When the bridge circuit has been balanced then, in accordance with one of the features 0f my invention, the motor current source by the deenergization of relays |08 and |02. Deenergization in the movement of switch cated, supplies a pulse of current quickly and yedectively to stop the motor when the'circuit has been rebalanced. The motor is maintained in its stopped position by a relatively low direct current, the motor being connected across the conductors 13S and i12 through the resistor llt.

The arrangement of the bridge circuit and variable resistors and the resistance value of the encircuited portion of the resistor it are such that when the ofi resistor 'it is switched into the bridge circuit, the circuit becomes balanced only when the scriber 92 is moved to its extreme left position, thereby to provide an indication that the receiver has been turned off. An indication that tlie telephone line is open, which is particularly desirable in the event the connection is made through a telephone exchange, is given by the location of the scriber 92 at its extreme right position. In the latter case the motor Sli operates the contact 96 of resistor 22 to an open circuit position.

Additional indications of the on and open circuit conditions are given by lamps let and i, respectively. When the radio is turned on, the lamp i3d is supplied with power, and under open circuit conditions, the lamp i812 is supplied with power.

When the radio is turned on, the lamp 32 connected to a low voltage secondary windin of transformer E23 through conductors i connection being effected by the closure of switch S88 operable by a relay winding The wind ing le@ is energized when the radio is turned on by the closure of a power circuit by a switch controlled by a cam 19e in such manner that the switch is closed except when the radio ii its oir position. In the off position, the switch is opened bythe cam, which is rotated to the on position by the motor 9d under the control of the bridge circuit. Power is supplied to the relay winding lei) from a suitable source, such as the 110 volt supply lines c2.

The open line condition is indicated by the illumination of lamp H82, which is connected across the power lines H85 by a switch blade igt controlled by a cam i558 under the open circuit condition. The cam and switch are so constructed and arranged that the switch blade closes an energizing circuit for the lamp when the motor gli is stopped in its offV position.

If desired, the scriber 92 may be so constructed and arranged that it is biased away from the record tape and is moved into contact with the tape whenever the radio receiver is turned on. The scriber may be moved into contact with the tape by a solenoid 26d which is supplied with power when the radio is turned on through a switch 232 closed by the relay winding it@ when the latter is energized. Power is supplied to solenoid 2B-ii from a suitable source, such as the direct current lines 3B.

If the solenoid Zlio is used, then the scriber is moved out oi contact with the tape in the oir position. However, the angular position of the scriber still indicates that the radio has been turned off.

' The use of the oil resistor 'it and the scriber in contact with the tape in the on position, enables variations in telephone circuit resistance to be checked. Ii the scriber solenoid it@ is used, then in order that the line resi-stance variation can be cheeked, there is provided a manually elosable switch Ebd which, when closed, energizes the relay lo@ independently of the cam controlled switch 192.

In accordance with another feature of the present invention, the apparatus is provided with means for visually indicating the network to which the radio station is connected. This means includes a plurality of network indicating lamps 2 lll, in this case ve, for indicating five networks and a lamp 2 l2 for indicating stations other than said five or more network stations. The illumination of the lamps is controlled by a druni type controller indicated as a whole by reference character 2MB, the angular position of which correspends to the tuning of the radio receiver, and which is angularly movable by the motor rlChis controller forms an important part oi my invention, as it, in eiTect, produces control impulses in a simple and effective way, which can be used for energizing lights or performing other desired functions.

rihe drum controller controls, in the embodiment of the invention illustrated, the supply of power to the lamps. It includes a drum having an outer shell ZIB of conducting material, upon which is mounted a card 2 I8 of insulating material having a series of longitudinally and angularly spaced apart perfcrations corresponding to the various stations. These perierations have angular lengths corresponding to the calibrated band widths of the stations to which they correspond, as will be described in greater detail shortly in conjunction with Figs. 2 to 5, inclusive.Y

The drum controller includes also a series of brushes 222 for each of the lamps, and a single brush 22d connected to ground (or a coininon conductor) through conductor 2255.

Power is supplied to the network indicating means through a transformer 22e having its primary winding 239 connected to a suitable source of power, such as the conductors d2. rIhe low voltage secondary winding 2152 of the transformer is connected to a conductor 23d common to the individual lamps and to a ground connection 23E.

The controller 2id controlling the energization of the lamps will now be described particular reference to Figs. 2 to 5, inclusive. It is preferably constructed as a unit with the adjustable resistor 22, which is shown in 2 and 3 as being Supported by a vertical plate 2de which, together with a somewhat smaller plate 2in, supports the controller. The supports and 262 are mounted upon a base plate 2M.

The controller is coupled to the motor Sic Vthrough a motor driven shaft The shaft Edt is drivingly connected to a combined drum and potentiometer driving shaft through a coupling sleeve 25d and a coupling 252.

rIhe outer shell ,'I of the drum controller isV preferably made of suitable conducting material, such as brass tubing. rIhe shell is not a complete tube, but rather is made with an arcuate extent somewhat greater than lSil" so that the perforated card 228 may be readily and detachably secured to it, and because only a portion of the potentiometer 22 is actually used. This portion of resistor 22 is preferably from 0 to about 6.00.@ ohms, corresponding to the used portion of resistor 2c. The shell is suitably secured, as by soldering, to an inner support 25.15 which is attached to the shaft 2553.

The card 2I8 is made of some suitable insulating material such as fiber paper or plastic. It is detachably secured to the drum shell 2&5 in such manner that it may be readily attached or detached. This is of importance, because the perforations 22o in the card must be calibrated with the radio receiver properly to indicate the aeut the shell by a pair of screws 258, only one of which is illustrated in Fig. `Il. The other end 26!! is bent around the opposite end of and attached to the insideof the shell by resilientrneans face of the shell. The resilient means includes a pair of springs 262 located near opposite axial ends of the shell and secured to the inside of the shell by small screws 264. The opposite ends of the springs are detachably attachedvto the end 26D of the card by a card holder bar 266, the bar being provided with apertures 268 near its op posite ends, enabling the bar easily to be hooked to the springs. The bar is secured t the card by a pair of spaced apart screws 210. The bar is guided and held against undesired displacement by a slot 212 in and locatednear the outer surface of the shell holding member 254.

The brushes 222 and 224 are mounted upon a brush holder indicated generally by reference movably supported abovethe shell 1n order that the brushes may be moved away cards or the like. Y

The brush holder 214 is movablysupported on a supporting shaft 216 secured at its opposite ends to the supporting plates 24U and to an extension supporting plate-218 secured to the upper end of supporting plate- 240.

The brushes are detachably secured to the brush holder by the two detachable parts 28D d 282 of the holder, between which the brushes 222 and 224 are securely held. Brushholder part 288 is movably mounted onl the supportingshaft 216 and brush holder part 282 is secured to part 280 as by a plurality of screws A284.

The brushes 222 comprise relatively long contact arms 222A made of suitable material, such as Phosphor bronze spring wire, and brush wires 222B secured to the ends of the contact arms and resiliently bearing againstthe card 2I8 o'r the shell 2|6, as the case may be. I f K The Contact arms and brushes are biased and held against the card and shell by suitable means, such as a snap spring 286, having one' end secured to the brush holder andV having its lc'rt'her end bent and provided with a semi-circular bend r288V adapted to nt about a stop pin" 298, therebyto hold the brush assembly in positin. The pressure with which the brushes are7 held against the' shell by spring 2861s adjusted byaserew e position of the snap spring 236 relative to the brush holder. Y

The longitudinal position of the brushes is adjustable by the desired location ofv apair of spacer collars 294 at opposite ends of the brush holder, and which are detachably secured to the supporting shaft 216. Y l

In the description of the operation ofthe ap-v paratus, it will be assumed that the radi; refceiver has been in operation andthat the recording and indicating apparatus has been stopped in a position corresponding to the staj tion to which the receiver is tuned and that the visual indicating means shows thenetwork affiliation of the station. At this timev the various switches and circuits are inthe conditions illustrated in Fig. l. The plug 46 is connected to a suitable source of alter'nat'ingl current volt'- age; the test switch |42 is' closed as' are th yirio- 75" @from Shen curring through switch blades I 84 and ll in their illustrated positions. The motor 6i) associated with the radio receiver is deenergzed, as is. the relay 80. Resistor 82 .is therefore short circuited by the switch 86 so that the resistor 20 is connected to the bridge circuit through the switch blade 66. Indicator 92 isin a position corresponding to the station tuned in and one of lamps 2I0 is illuminated.

Assuming now that the user of the radio tunes in another station.- then the motor 6U and the relay )..are energized. The former operates the tuning condenser 10-of the electronic control device and the voltage of the br1dge is applied to the grids of the vacuum tubes H6 and H8 with the result that current ows through thevwinding |l2 Aof relay |08. The movable switch blade H0 of the source of alternating current, motor to rotate. The motor therefore operates to move the scriber 92, Yto adjust resistor Y22 and tomove the visual indicator controller 2id.

continues to adjust resistor 2Q W has been adjusted to a value balancing the resistor 20. When thus adjusted,v the bridge output returns to zero and the relay I ll8 is deenergized. The latter efects the deenergization -of vrelay motor and hold it stopped. stops,lthe scriber 92 also stops and in a position corresponding to the ratio station to which the receiver is tuned.

a circuit including the lamp, the correspondingbrush 222, perforation 2.2iA and the 216 The lamp indicates the network afliation ofthe station tuned nation @manipV 212.

The controller drum and perforatedcard provide accurate indication of stations received close together on the frequency band because they usually are on dierent networks so that the perforations are axially displaced.

Only about one-half of the controller drum and resistors 2d and 22 are used because the stations tuned in on the receiver are recorded only when the scriber Q2 is moved in one directionthereby to avoid back lash. For the same rea.- son, the motor t@ of the electronic control associated with receiver, which has a scriber associated with it (not shown) is only stopped for one direction of variation of condenser lo.

When the tuning of the radio receiver is again varied, the operation is repeated as heretofore described, with the result that the scriber 92 and drum controller 2HE. are again operated to new positions corresponding to the station tuned in and network afliiliation of the station. A continuous and accurate indication and record are thus made of the stations to which the receiver is tuned and a visual indication is provided of the network.

When the radio receiver is turned oif, the relay 64 is deenergized (with a brief time delay if the power source includes a rectier tube having an indirectly heated cathode) and its switch 66 connects the off resistor 'ill in the bridge circuit. The bridge circuit is thus unbalanced (and when the time delay type operation occurs, the bridge is unbalanced by operation of the motor E for a brief interval) and fthe motor 95 again energized to adjust resistor 22 until it balances the bridge for the eiective value ci resistor iii in the bridge circuit. As heretofore indicated, this balance occurs when the scriber 92 is at 4the extreme left of the tape lii. In the off position, the light IS is extinguished to give a visual indication. The light is extinguished by the opening of switch i92 by cam i913, and the subsequent opening of switch |88 upon deenergization of relay winding |90. At the same time solenoid Zii is deenergized and the scriber lifted 'from the tape-this providing a record of the oif position.

When the receiver is turned on, the relay Gli is energized to disconnect resistor 'ifi from the: bridge circuit and to connect resistor 2G to it. This unbalances the bridge circuit, as does the connection of resistor B2 to the bridge circuit by relay 8B, which is energized along with motor Sii to hunt for the station tuned in by the receiver. The motor si! is again energized because of the unbalance of the bridge circuit and it operates to adjust resistor 22, to move scriber s2 to indicate and record the tuning of the radio receiver i to move the drum control visually to indicate the network.

In the event the telephone line is opened, for example inadvertently at a telephone exchange through which the line extends, the scriber 92 is operated to its extreme right position to indicate the open circuit condition. When the telephone line is opened, an innite resistance is placed in one leg of the bridge with the result that the bridge is unbalanced and the motor 9d is energized to adjust resistor 22 until it is in an open circuit position, whereat the bridge is again balanced and the motor ed stopped.

An indication of short wave recep-tion is also provided. When the receiver is turned to short wave reception, the motor operates continuously to vary the resistor 2%. As a result the bridge circuit is continuously unbalanced and motor gli continuously energized to oscillate the scriber 92 back and forth across the tape.

f* In order to ascertain if there hasbeen a change in line resistance when the radio receiver is in its oif position, the switch 256i may be closed so that the scriber will make a record. If the record is not at the normal oii position, an indication of resistance variation is given and this may be compensated for by adjustment of line balancer resistor 28.

While but a single embodiment of tion has been described in detail, it should be understood that these details are not intended to be limitative of the invention except insofar as set forth in Vthe accompanying claims. Insofar as modifications of the invention are concerned, it should perhaps be noted that the resistor 2! may be varied by means other than that described. For instance, the variation could be eected by mechanically coupling the movable contact 52 directly to the tuning control of the receiver. Oththe invener arrangements and types of impedance means may also be used.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: i

1. Apparatus for indicating at a central station the tuning of a radio receiver positioned at a remote point from the central station, including in combination, indicating means including a movable member, a unidirectional motor operatively connected to said movable member for moving said member, a balanced bridge circuit adapted to be unbalanced by changes in tuning of the receiver and to be rebalanced by operation of said motor, said circuit comprising a variable resistor comprising one arm ci the bridge circuit positioned at the remote point and variable in response to the tuning of the receiver to unbalance the circuit the other three arms of the bridge circuit being positioned at the central station, one of said three arms including a variable resistor variable by said motor to rebalance the circuit, balanced amplifying means diiferentially connected to the bridge circuit, and a relay connected to the output of said amplifying means and controlling the position of the motor in response to unbalances in the bridge circuit to move said movable member into diierent positions corresponding to the variations in the variable resistor positioned at the remote point due to the tuning of the receiver.

2. Apparatus for indicating at a central recording station the tuning of a radio receiver located at distant point, including in combination, indicating means at the central station including a movable member, a unidirectional alternating current motor at the central station operatively connected to said movable member for moving said member, a balanced bridge circuit extending from the distant point to the central station adapted to be unbalanced by changes in tuning of the receiver and to be rebaianced by operation of said motor, said circuit comprising a Variable resistor in the bridge circuit variable in response to the tuning of the receiver to unbalance the circuit and a variable resistor in the bridge circuit variable by said motor to rebalance the circuit, balanced amplifying means differentially connected to the bridge circuit, a relay having a winding connected to the output of said amplifying means, a switch operable by said relay for connecting the motor to an alternating current source whenever the bridge circuit is unbalanced thereby to move said movable member into different positions corresponding to the tuning of the receiver, means 13 operable by said switch when the motor is disconnected from the alternatingl current source for dynamically stopping. the motor, two other resistors at the distant point, means operable in response to a change in tuning for connecting one of said other resistors in said balanced circuit temporarily when the tuning is changed thereby to effect operation of said indicating means by said motor each time the tuning is changed to provide greater accuracy, and means operable in response to the operative condition of the receiver for disconnecting said irst mentioned variable resistor and connecting the second other resistor to said balanced circuit when the receiver is turned oft.

3. Apparatus for indicating the tuning of a radio receiver, including in combination, indicating means including a movable member, power means operatively connected: tosaid movable member for moving said member, means including a balanced circuit comprising circuit balance changing means operable in response to the tuning or" the receiver and circuit balance changing means operated by said power means for controlling the operation of said power means, other balance changing means, and means for connecting said other balance changing means to said circuit only during the time the rst mentioned balance changing means is operated.

4. Apparatus for indicating the tuning of a radio receiver, including in combination, indicating means including a movable member, power means operatively connected to said movable member for moving said member, means including a balanced circuit comprising iirst variable circuit balance changing means operable in response to the tuning of the receiver and second variable circuit balance changing means operated by said power means for controlling the operation of said power means, third balance changing means, means for connecting said third balance changing means to said circuit only during the time the first mentioned balance changing means: is operated, fourth balance changing means, and means responsive to the operative condition of the receiver for connecting said iirst variable balance changing means in said balanced circuit when the receiver is operative and for connecting said fourth variable balance changing means in said balanced circuit when the receiver is out of operation.

5. Apparatus for indicating at a central station the tuning of a radio receiver positioned at a remote point from said central station, including in combination, indicating means including a movable member, power means including a unidirectional motor operatively connected to said movable member for moving said member, and means including a balanced circuit comprising circuit balance changing means positioned at the remote point and operative in response to tuning of the receiver and circuit balance changing means positioned at the central station and operated by said motor for controlling the operation of said motor to move said movable member to different positions corresponding to the tuning of the receiver, said second mentioned balance changing means including an open circuit position whereby an open circuit condition existing between the central station and the remote point may be indicated.

6. Apparatus for indicating at a central station the tuning of a radio receiver positioned. at a remote point from said central station, 1ncluding in combination, indicating means including a movable member, a unit operatively con:- nected to said movable member for moving said member, means including a balanced circuit comprising circuit balance changing means positioned at the remote point and operable in response to tuning of the receiver and circuit' balsponding to the tuning of the receiver, said second mentioned balance changing means including an open circuit position whereby an open circuit condition existing between the central station and the remote point may be indicated, and means associated with said motor for visually indicating said open circuit condition.

7. Apparatus for recording at a central station the tuning of a receiver positioned at some distance therefrom upon' a movable tape or the like, including in combination, a recording member mounted for movement to engage and be disengaged from the tape, means operable in response to placing of the receiver in operation for effecting movement of the said member to engage the tape in order to provide a record of the operation of said receiver, a circuit interconnecting said central station and said remote point, and means operable independently of said last mentioned means for eiecting movement of said member to engage the tape, the operation of said last mentioned means causing the movement of the recording member for a distance which is dependent upon variations in said circuit impedance so as to provide an indication of said variation.

8. Apparatus for recording at a central station the tuning of a receiver positioned at some distance therefrom upon a movable tape or the like, including in combination, a recording member mounted for movement to engage and be disengaged from the tape, means including a solenoid energizable in response to placing the receiver in operation for effecting movement of the said member to engage the tape in order to provide a record of the operation of said receiver, a signal line interconnecting said central station and said remote point, and means operable independently of said last mentioned means for energizing said solenoid for eilecting movement of said member to engage the tape, the operation of said last mentioned means causing the movement of the recording member for a distance which is dependent upon variations in the resistance of said signal line so as to provide an indication of said variations.

9. Apparatus for recording at a central station the tuning of a receiver located remote from the apparatus upon a movable tape or the like, including in combination, a recording member mounted for movement to engage and be disengaged rom the tape and for transverse movement along said tape to record data, means including a circuit coupling the apparatus to the receiver, a cam switch, a solenoid, means including said cam switch for energizing said solenoid in response to placing the radio in operation for effecting movement of the said member to engage the tape in order to provide a record of the operation of said receiver, a signal line interconnecting said central station and the remote location, means including a manually operable switch for energizing said solenoid independently of said cam switch for effecting movement of said member to engage the tape, and means for mov- 15 ing the recording member transversely of the' tape uponrthe operation of said independently operated means for a distance which is dependent upon variations in the resistance of said si9` nal line so as to provide an indication or said variations.

JAMES Gr. BLACK.

References Cited n the 111e of this patent Number CII.

Number Name H Date K Doyle et al May 31, 1938 Watkins Dec. 20, 1938 Elder et al Oct. 10, 1939 Graham Apr` 7, 1942 Keller May 12, 1942 Woodruff Dec. 22, 1942 Ridings et al May 14, 1945 Allen Feb. 5, 1946 Potter Apr. 2, 1946 Girard Jan. 27, 1948 Clark, Jr. Apr. 6, 1948 Grepe Oct. 10, 1950 Field Nov. 14, 1950 Dueringer Mar. 13, 1951 FOREIGN PATENTS Country Date France Apr. 2, 1927 

